1. Technical Field
Various embodiments of the present invention relate to a circuit device, an oscillator, an electronic apparatus, a moving object, and so on.
2. Related Art
In the past, there has been known an oscillator such as an oven controlled crystal oscillator (OCXO), and a temperature compensated crystal oscillator (TCXO). For example, the OCXO is used as a reference signal source in a base station, a network router, a measurement device, or the like.
As the related art of such an oscillator, there exists, for example, a technology disclosed in JP-A-2015-82815. In the related art, an aging correction of the oscillation frequency is performed in order to increase the accuracy of the oscillation frequency. Specifically, there are disposed a storage adapted to store correspondence relationship information between a correction value of a control voltage of the oscillation frequency and elapsed time, and an elapsed time measurer. Further, an aging correction is performed based on the correspondence relationship information between the correction value and the elapsed time stored in the storage, and the elapsed time measured by the elapsed time measurer.
As described above, in the oscillator such as the OCXO or the TCXO, there is a demand for an increase in accuracy of the oscillation frequency of the oscillation signal.
In such an oscillator, in order to obtain the oscillation frequency higher in accuracy, the OCXO having a resonator the temperature of which is controlled by a thermostatic oven is preferable. In the OCXO, although the temperature of the resonator is controlled, in reality, if the ambient temperature of the thermostatic oven varies, the temperature of the resonator varies due to the influence of the variation of the ambient temperature of the thermostatic oven, and the oscillation frequency slightly varies. Therefore, in order to obtain the oscillation frequency higher in accuracy, the temperature compensation is necessary. The temperature compensation is for reducing the variation in oscillation frequency due to the temperature variation of the resonator. Specifically, in the temperature compensation, the temperature of the resonator is measured by a temperature sensor, and the control is performed so that the oscillation frequency becomes constant based on the temperature thus measured. Although the temperature sensor is provided to, for example, a circuit device for generating an oscillation signal, the circuit device (the temperature sensor) is disposed in the thermostatic oven so as to be able to measure the temperature of the resonator.
However, as described above, the temperature is basically controlled in the thermostatic oven as described above. Therefore, although affected by the ambient temperature, if the temperature sensor incorporated in the circuit device is used alone, the variation range of the sensing temperature due to the variation in the ambient temperature becomes small, and the temperature compensation with high accuracy cannot be achieved. For example, the sensing voltage of the temperature sensor is A/D converted by an A/D conversion circuit, and the temperature detection data is used for the temperature compensation. In this case, since the variation range of the sensing voltage becomes extremely small with respect to the input full scale of the A/D conversion circuit, the resolution of the A/D conversion circuit becomes low (the code variation range with respect to the variation range of the sensing voltage becomes small), and there is a possibility that the temperature compensation with high accuracy cannot be achieved.